Orientale Impact Basin for the Cover of Science

This print-resolution still image was created for the cover of the October 28, 2016 issue of Science. It features a free-air gravity map of the Orientale impact basin based on data returned by the Gravity Recovery and Interior Laboratory (GRAIL) mission.

Orientale is about 930 kilometers wide and lies on the western limb of the Moon as viewed from Earth. It's the Moon's youngest and best-preserved large impact basin, formed about 3.8 billion years ago at the end of the conjectured Late Heavy Bombardment. A paper in Science by Maria Zuber et al. uses the GRAIL data to shed new light on the basin's geology, while a second paper by Brandon Johnson et al. describes a computer simulation of the basin's formation constrained by that data.

The shaded relief in this image is not a photograph. It's a very accurate computer rendering based on a digital model of the terrain. The model is derived from a digital elevation map called SLDEM2015. This map combines data from the laser altimeter (LOLA) on NASA's Lunar Reconnaissance Orbiter (LRO) with stereo imagery from the Terrain Camera on the Japan Space Agency's SELENE spacecraft.

The angle of the virtual Sun was chosen to throw Orientale's terrain into high relief — it's just after sunrise at Orientale, about a day past full Moon. The camera is on the western terminator (day/night line) looking north.

The colorful part is the gravity anomaly based on measurements by GRAIL. Red indicates areas of higher gravity, or excess mass, and blue indicates lower gravity or areas of mass deficits. The GRAIL data reveals the structure of the basin beneath the surface. The red in the center of the basin, for example, shows that the crust is particularly thin there, and that denser mantle material is closer to the surface.